Iwasaki A, Ishito T
Med Phys. 1984 Nov-Dec;11(6):755-63. doi: 10.1118/1.595576.
Using the O'Connor density scaling theorem, two basic equations have been derived to express scatter dose calculations in both homogeneous and heterogeneous phantoms: (i) the differential scatter-air ratio for calculating the frontscatter, and (ii) the differential backscatter factor for calculating the backscatter. In the derivation of both equations the relative electron density along the line between the scattering element and the calculation point has been averaged to account for scatter attenuation. Each equation expresses the amount of front or backscatter at the point of calculation per unit primary dose, per unit relative electron density, per unit volume at the scattering element. Primary dose calculations in both a homogeneous and a heterogeneous phantom have been carried out using a simple exponential attenuation law. Except in the area of or near interfaces and the area around field borders where there is electron disequilibrium, satisfactory dose calculations have been obtained using the primary and scatter dose calculation procedure for experiments done with Co-60 gamma rays in homogeneous soft tissue phantoms and in heterogeneous cork and aluminum phantoms.
利用奥康纳密度缩放定理，已推导出两个基本方程，用于表示均匀和非均匀体模中的散射剂量计算：（i）用于计算前散射的微分散射-空气比，以及（ii）用于计算后散射的微分后散射因子。在这两个方程的推导过程中，对散射元件与计算点之间连线上的相对电子密度进行了平均，以考虑散射衰减。每个方程表示在计算点处每单位原射线剂量、每单位相对电子密度、散射元件处每单位体积的前散射或后散射量。在均匀和非均匀体模中，使用简单的指数衰减定律进行了原射线剂量计算。除了在界面处或其附近以及射野边缘周围存在电子不平衡的区域外，使用原射线和散射剂量计算程序，对在均匀软组织体模以及非均匀软木和铝体模中用钴-60伽马射线进行的实验，已获得了令人满意的剂量计算结果。
